1. Technical Field of the Invention
The present invention relates generally to a starter which may be employed in starting an automotive engine, and more particularly to a compact structure of such a starter equipped with a pinion carrier which is to be shifted by a magnetic attraction, as transmitted from an electromagnetic switch through a shift lever, to establish engagement of a pinion with a ring gear jointed to an object to be started.
2. Background Art
FIG. 6 illustrates one of typical engine starters, as disclosed in Japanese Patent First Publication No. 9-209890 (U.S. Pat. No. 5,898,229). The starter includes an electric motor 100, a clutch 110, an output shaft 120, a spline tube 130, an electromagnetic switch 150, and a pinion 140. The motor 100 produces torque which is transmitted to the output shaft 120 through the clutch 110. The spline tube 130 is fitted on an outer periphery of the output shaft 120 through helical splines. The pinion 140 is formed integrally on the spline tube 130. When energized, the electromagnetic switch 150 produces a magnetic attraction which moves a shift lever 160 to push the spline tube 130 toward an internal combustion engine (i.e., rightward, as viewed in the drawing) to bring the pinion 140 into engagement with a ring gear 170 of the engine.
The above structure of the starter, however, has the following drawbacks.
The pinion 140 and the spline tube 130 are, as described above, formed integrally with each other and made of material such as iron which is relatively high in specific gravity and mechanical strength. A total mass of the pinion 140 and the spline tube 130 will, thus, be high. When it is required to increase the distance L between an engine-mount surface of an starter housing 180 and the static position of the pinion 140 (i.e., the top end surface of the pinion 140), the length of the spline tube 130 needs to be increased, thus resulting in an increase in mass of the spline tube 130, which will require an increase in power (i.e., the magnetic attraction) of the electromagnetic switch 150 for moving the spline tube 130 through the shift lever 160. This results in an increased size of the electromagnetic switch 150.
The shift lever 160 has an end placed in abutment with a surface 131 of a flange of the spline tube 130 through a small contact area, so that the pressure acting on the surface of the end of the shift lever 160 will be high. Therefore, in the case where the shift lever 160 is made of resin for saving the weight and production cost thereof, it will result in an increase in mechanical wear of the end of the shift lever 160 resulting from the friction with the rotating surface 131 of the spline tube 130. This results in a decrease in amount by which the shift lever 160 moves the pinion 140 toward the engine, which may lead to a failure in engagement of the pinion 140 with the ring gear 170.